//$Id: FastHashMap.java 167 2006-03-15 22:28:40Z csuconic $
/*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 1999-2002 The Apache Software Foundation. All rights
* reserved.
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* modification, are permitted provided that the following conditions
* are met:
*
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* distribution.
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* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
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// This class was taken from Apache commons-collections -
// I made it final + removed the "slow" mode...
package org.jboss.serial.util;
import java.io.Serializable;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
/**
* <p>A customized implementation of <code>java.util.HashMap</code> designed
* to operate in a multithreaded environment where the large majority of
* method calls are read-only, instead of structural changes.
* Read calls are non-synchronized and write calls perform the
* following steps:</p>
* <ul>
* <li>Clone the existing collection
* <li>Perform the modification on the clone
* <li>Replace the existing collection with the (modified) clone
* </ul>
* <p><strong>NOTE</strong>: If you are creating and accessing a
* <code>HashMap</code> only within a single thread, you should use
* <code>java.util.HashMap</code> directly (with no synchronization), for
* maximum performance.</p>
*
*/
public final class FastHashMap implements Map, Serializable {
// ----------------------------------------------------------- Constructors
/**
* Construct a an empty map.
*/
public FastHashMap() {
super();
this.map = new HashMap();
}
/**
* Construct an empty map with the specified capacity.
*
* @param capacity The initial capacity of the empty map
*/
public FastHashMap(int capacity) {
super();
this.map = new HashMap(capacity);
}
/**
* Construct an empty map with the specified capacity and load factor.
*
* @param capacity The initial capacity of the empty map
* @param factor The load factor of the new map
*/
public FastHashMap(int capacity, float factor) {
super();
this.map = new HashMap(capacity, factor);
}
/**
* Construct a new map with the same mappings as the specified map.
*
* @param map The map whose mappings are to be copied
*/
public FastHashMap(Map map) {
super();
this.map = new HashMap(map);
}
// ----------------------------------------------------- Instance Variables
/**
* The underlying map we are managing.
*/
private HashMap map = null;
// --------------------------------------------------------- Public Methods
/**
* Remove all mappings from this map.
*/
public void clear() {
synchronized (this) {
HashMap temp = (HashMap) map.clone();
temp.clear();
map = temp;
}
}
/**
* Return a shallow copy of this <code>FastHashMap</code> instance.
* The keys and values themselves are not copied.
*/
public Object clone() {
return new FastHashMap(map);
}
/**
* Return <code>true</code> if this map contains a mapping for the
* specified key.
*
* @param key Key to be searched for
*/
public boolean containsKey(Object key) {
return map.containsKey(key);
}
/**
* Return <code>true</code> if this map contains one or more keys mapping
* to the specified value.
*
* @param value Value to be searched for
*/
public boolean containsValue(Object value) {
return map.containsValue(value);
}
/**
* Return a collection view of the mappings contained in this map. Each
* element in the returned collection is a <code>Map.Entry</code>.
*/
public Set entrySet() {
return map.entrySet();
}
/**
* Compare the specified object with this list for equality. This
* implementation uses exactly the code that is used to define the
* list equals function in the documentation for the
* <code>Map.equals</code> method.
*
* @param o Object to be compared to this list
*/
public boolean equals(Object o) {
// Simple tests that require no synchronization
if (o == this)
return true;
else if ( !(o instanceof Map) )
return false;
Map mo = (Map) o;
// Compare the two maps for equality
if ( mo.size() != map.size() )
return false;
java.util.Iterator i = map.entrySet().iterator();
while ( i.hasNext() ) {
Map.Entry e = (Map.Entry) i.next();
Object key = e.getKey();
Object value = e.getValue();
if (value == null) {
if ( !( mo.get(key) == null && mo.containsKey(key) ) )
return false;
}
else {
if ( !value.equals( mo.get(key) ) )
return false;
}
}
return true;
}
/**
* Return the value to which this map maps the specified key. Returns
* <code>null</code> if the map contains no mapping for this key, or if
* there is a mapping with a value of <code>null</code>. Use the
* <code>containsKey()</code> method to disambiguate these cases.
*
* @param key Key whose value is to be returned
*/
public Object get(Object key) {
return map.get(key);
}
/**
* Return the hash code value for this map. This implementation uses
* exactly the code that is used to define the list hash function in the
* documentation for the <code>Map.hashCode</code> method.
*/
public int hashCode() {
int h = 0;
java.util.Iterator i = map.entrySet().iterator();
while ( i.hasNext() )
h += i.next().hashCode();
return h;
}
/**
* Return <code>true</code> if this map contains no mappings.
*/
public boolean isEmpty() {
return map.isEmpty();
}
/**
* Return a set view of the keys contained in this map.
*/
public Set keySet() {
return map.keySet();
}
/**
* Associate the specified value with the specified key in this map.
* If the map previously contained a mapping for this key, the old
* value is replaced and returned.
*
* @param key The key with which the value is to be associated
* @param value The value to be associated with this key
*/
public Object put(Object key, Object value) {
synchronized (this) {
HashMap temp = (HashMap) map.clone();
Object result = temp.put(key, value);
map = temp;
return (result);
}
}
/**
* Copy all of the mappings from the specified map to this one, replacing
* any mappings with the same keys.
*
* @param in Map whose mappings are to be copied
*/
public void putAll(Map in) {
synchronized (this) {
HashMap temp = (HashMap) map.clone();
temp.putAll(in);
map = temp;
}
}
/**
* Remove any mapping for this key, and return any previously
* mapped value.
*
* @param key Key whose mapping is to be removed
*/
public Object remove(Object key) {
synchronized (this) {
HashMap temp = (HashMap) map.clone();
Object result = temp.remove(key);
map = temp;
return (result);
}
}
/**
* Return the number of key-value mappings in this map.
*/
public int size() {
return map.size();
}
/**
* Return a collection view of the values contained in this map.
*/
public Collection values() {
return map.values();
}
public String toString() { return map.toString(); }
}